Glass is treated as an indispensable component in a variety of technological and industrial fields including imaging and optical devices such as monitors, cameras, video tape recorders (VTRs) and mobile phones, transportation equipment such as vehicles, a variety of dishes, and construction facilities. Accordingly, glass products having a variety of properties that meet the requirements of respective industrial fields are manufactured and used.
In particular, currently, chemically toughened thin glass is used for a cover glass or a display glass in display devices, such as organic light-emitting diode (OLED) displays, liquid crystal displays (LCDs), plasma display panels (PDPs) and field emission displays (FEDs).
Glass toughening methods generally include a physical toughening method and a chemical toughening method. The physical toughening method, also referred to as air-cooled toughening, is mainly applied to safety glasses for vehicles. The chemical toughening method can be applied to a thin glass sheet having a complicated shape or a thickness of about 2 mm or less. The chemical toughening method improves the strength and hardness of a glass by substituting alkali ions having a smaller ion radius (generally Na ions) with alkali ions having a larger ion radius (generally K ions) in certain conditions. The ion exchange generates large compressive stress on the glass surface, thereby increasing the strength and hardness of the glass.
A brief description will be given below of a method of manufacturing chemically toughened glass.
First, a raw glass plate is subjected to flattening, and subsequently is cut according to an intended shape and size using a cutting machine. However, this cutting process may cause deformation or stress to the glass through mechanical processing, thereby having an adverse effect on the reliability of products. In addition, errors in the cutting process may cause some portions of the raw glass plate to be discarded, thereby lowering the yield.
First cleaning is carried out to remove glass powder or impurities from unit pieces of glass that are formed through the cutting of the raw glass plate. Top and bottom edges of the unit pieces of glass are chamfered using a grinder. Second cleaning is carried out to remove glass powder or abrasive powder from ground products. The cleaned unit pieces of glass are dried. The surfaces of the unit pieces of glass are chemically toughened by a chemically toughening process as follows.
A unit piece of glass is immersed into a bath in which a potassium nitrate (KNO3) solution heated to a temperature ranging from 450 to 500° C. is contained. The unit piece of glass is maintained in this state for 3 hours or longer, such that toughening occurs through ion exchange. The unit piece of glass taken out of the bath is subsequently subjected to cleaning and drying.
However, this method of manufacturing chemically-toughened unit pieces of glass has the drawback of low productivity in the manufacture of the chemically-toughened glass since a raw glass plate is cut into a predetermined size before being chemically-toughened.
Accordingly, after the chemical toughening, the raw glass plate is cut into unit pieces of glass using a water jet, a subscriber device, a laser, or the like. However, according to this method, deformation or stress may occur in the glass due to the mechanical processing, thereby causing an adverse effect on the reliability of products. In addition, some portions of the glass are discarded due to errors in the cutting process, thereby lowering the productivity of the toughened glass, which is problematic.
In order to overcome this problem, Korean Patent Application Publication No. 10-2011-0086475 disclosed a method of cutting a toughened raw glass plate. This method includes forming a photoresist pattern on the toughened raw glass plate except for portions along which the toughened raw glass plate is to be cut, cutting the toughened raw glass plate along the portions to be cut by wet etching, and removing the photoresist. However, since this method includes additional processes for cutting the raw glass plate, such as the photoresist processing and the etching, the manufacturing cost of the toughened glass is increased. In addition, the use of hydrofluoric acid (HF), sulfuric acid (H2SO4), or the like causes environmental contamination, which is problematic.
In addition, Korean Patent No. 10-1022591 disclosed a method of cutting a raw glass plate. According to this method, both surfaces of the raw glass plate are patterned into a chemically-toughened area and a non-chemically-toughened area, followed by ion exchange. Afterwards, the raw glass plate is cut along some portions thereof in which the ion exchange has not been carried out. However, micromachining is difficult according to this method. That is, it is difficult to precisely form the pattern with a width less than 1 mm. In addition, the problem of the matching of the patterns on the both surfaces may occur. During the ion exchange, an ion exchange solution may flow over the patterns, thereby causing defects during the cutting. Furthermore, when this method is applied to a large glass plate, stress generated by the localized ion exchange may cause a problem, such as warping, in the glass plate.
The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.